Stabilized ethyl cellulose hot melt compositions



R. M.'KRAJEw'sKl ETAL' 2,887,396

STABILIZED ETHYL cELLuLosE Hoff MELT coMPosITroNs Filed 'Juiy s'o, 1957 May 19,)v 1959 Unite Staes STABILIZED ETHYL CELLULGSE HOT' MELT 'COMPOSITIONS' Richard M. Krajewski' and Harold c.. Kelly, Midland,

Mich., assignors to The Dow Chemical Company, Midland,-Mich., a corporation of Delaware Application July 30,A 1957, Serial No; 675,135iv 19 Claims. (Cl. V106-177)gY This invention relates to. stabilizedV ethyl. cellulose-containingcompositionsy that are particularly adapted. to.'y be` utilized, aszhot melts in order to be appliedA to desired articles, such as metal parts and the like, to form;tough,.

protective coatings that can be. easily-strippedor peeled clean-from the coated articles. to ready them'for'l use. The present application is a continuation-in-partof'the copending application for United States Letters Patent having Serial Number 627,124, now abandoned, which wasy tiled on December4 10, 1956.

Ethyl cellulose has been employed extensively and with signicant advantage in various hot melt compositions'in orderto impart toughness. and flexibility to the resulting.

coatings, thaty are obtainable therewith. While the forminlationsof such compositions may be widely varied toy meet. particular requirements, they may typicallycontam between about.20 and 30 percentby weight-of the celluloseether (or. more or less in specic instances)v in combination with various resins, mineral oils., waxesplasti cizers and the like that are conventional for such formulations. In addition to their usesl for the readily removable and-usually more; or lesstemporary protective coating; of metal parts and the like, such compositionshave found. widespread. application in thepaper coating and allied elds. In compositions that are adapted for paper coatingfand the like, it is not unusual to utilize as. littleas about. 10. percent by weight of the cellulose ether. U.S.

Patent No. 2,394,101; Canadian Patent No. 525,610 and' British Paten-t N'o. 734,968 contain docent illustrations of' various ethyl cellulose hoty melt compositions.

The hot melt' compositions of ethyl cellulose are generally applied, as in hot dip procedures, at elevated temperatures which' may range, for example, from about-140 tol 190 C. When metal articles are being coated it isv common to utilize the upper portion of the indicatedi range', say.` fromabout 175 to 19.0 C. And, inmany instances; especially when ,metall articles are `being hoti dipped, it is not uncommon. for. the hot melt composition.

hot` melt compositions-.againstthermaldegradation by thel incorporation therein of. various antioxidant and. other stabilizing additaments.` For example, thetype of degradatior'rtllatv isknownas' acid' catalyzed hydrolytic degra dati'onf. may be; largely minimized'v or. overcomeby incorporating various acid accepting epoxy compoundsv inithe;y ethylv cellulose: composition. Likewise, oxidative degradationmay be provided for and its eiects substantially.; nullifiedzby-A Vincorporatingsinit the )ethyl cellulose hot. melt'. composition any.: one iorzmore'; of a.y great number.'y of oxidation: inhibitors: that-lI are known tot be.; effective for.

thepurpose. Among thesmost'utilezand beneiicial of the antioxidant materials that are available for employment in1ethylA cellulose hot melt .compositions'is 2,2'.methylene bis (4-methy16;-tert..butyli phenol ):.v source-of this material :designatess itto `tlietrade ras ,Anti oxidant 2,246.

The utilization -of-k 2,2fmethylenefbis (4-methyl-6-.tertbutyl phenol);.in:a. conventional .manner as an. antioxidant.

ingghighly diseolored; uponiexposure for prolonged periods to. heat at elevated'temperatures. This, of course, limits the general utility of the material for employmentias an;

ant-ioxidant.in-.rethyl.cellulose'hot melt compositions that are intendedto` prov-ide relativelyy clearV and transparent coatings. And, as canr.be-appreciated,.many of the most` desirable applicationsforrethyl cellulose hot melt coatings arebased. upon an'. achievement of, relative transparencyl andfsubstantial freedomfronrdiscoloration in ythe coating.l Thisis notonly fonaesthetic reasons, as important as they maybe, but. due tothe. fact that, many articles, suchas.-

metal parts andzthe like, ,bear legendsand'other identify-v ing marks '(such as numbers) on their surfaces which, asv a practical matter, are very. much desired to. remain legiblydiscernible.through whatever temporary protective coating may be, .appliedf.thereover..

Therefore, it would be4 a. greatladvantage to. provide stabilized ethyl' cellulosehot'rnelt coating compositionsl butyl phenODaS-.an antioxidant. ingredient without beingj susceptiblelto becomiugintolerabl'y discolored upon prolonged.y exposure ofthe composition to heat at elevated'.

hott dipping, temperatures.

Thisfdesideration'. and. other advantages an'dbeneiits may-be realizedfy in accordance with the practicev ofthe presentfinvention which. provides ethyl cellulose-containing` hot; melt:y coating,y compositions: that` are formulated with thefusualresinous,oleaginolls,plasticizing, and other beneficial; composition-modifying ingredients and which contain, as stabilizinggingredientstherefor, `a combination of.` minor; proportions. each of. (Aflr ZsZ-methyleneabis (4- methyle6+tert..b.utyl phenol) (B). an acid-accepting epoxy compound; and (C) a neutral (or substantially neutral) organic phosphite compound that is selected from the group consisting, of` alkylphosphites, halogen substituted alkyl phosphites, aryl phosphites, halogen substituted aryl phosphites, mixed alkylaryl phosphites, mixed halogen substituted alkyl-aryl phosphites and mixtures thereof. Advantageously, between 0.005 and 5 percent by weight of the 2,2methylenebis.(4methy16tert.-buty1 phenol); betweenabout 0.1' and'lO percent by Weight of the acidaccepting epoxyl compound; and between about 0.1 and 2.0 percent by weight of the neutral phosphite compound; each based orl theweight of the composition, may be. incorporated. inthe. hot melt composition. More advantageously, amountsbetween about 0.05 and 4.0 percent` by weight: o'the former antioxidant material; betweenabout. 2'.0` and. 8.0,percent by weight of the acidaccepting epoxycompound; and between about 0.1 and .0.5. percent by weight'. ofi the last-mentioned neutral organc'zphosphite. compound may be employed. In many One: commercial.

instances, it may be found desirable to utilize proportions by weight of the antioxidant; epoxy compound and phosphite that are in the weight ratio of 0.4-4z10-30z1, respectively (oftentimes in the neighborhood of a combined total of about 4 to 7 percent by weight of the composition), within the indicated ranges of each of the stabilizing ingredients, particularly when such ratio is about 1:20:1.

It is usually suitable in the practice of the invention to employ an organic phosphite compound of the type that has been referred to in which the alkyl and aryl groups that may be involved independently contain from 2 to 10 and from 6 to 16 carbon atoms, respectively, in their structures. Equivalent structural characteristics are also applicable to the alkyl and aryl groups in mixed alkyl-aryl phosphites. Tricresyl phosphite, 2-ethylhexyl octylphenyl phosphite, tris(2-chloroethyl) phosphite, triisooctyl phosphite, tris(2ethylhexyl) phosphite, trihexyl phosphite, tri-l-naphthyl phosphite, tri-ortho-xenyl phosphite, triphenyl phosphite and tri-para-tertiarybutyldiphenyl phosphite are typical of the organic phosphite compounds that may be utilized satisfactorily. Additional suitable neutral phosphites may be similar to or identical with the other varieties of such compounds that have been illustrated in the disclosure of Canadian Patent No. 517,031.

Practically any of the acid-acceptingepoxy compounds may be utilized in the stabilized hot melt compositions of the present invention provided they are compatible in and with the particular system being stabilized. As will be appreciated by those who are skilled in the art, the determination of the compatibility of a particular substance which may be contemplated and intended as an ingredient for a hot melt composition may be simply and readily arrived at by easily performed tests. A wide variety of suitable acid-accepting epoxy compounds are known to the art and are readily available for utilization in the practice of the present invention. Included especially in this category may be such acid-accepting epoxy compounds as diglycidyl ethers of various polyglycols, particularly those polyglycols that are derived from con-v densation of say 8 to 40 moles of ethylene oxide or the like per mole of polyglycol product; diglycidyl ethers of glycerol and the like; metallic epoxy compounds; (such as those conventionally utilized in and with vinyl chloride polymer compositions) epoxidized ether condensation products; diglycidyl ethers of bisphenol A (4,4dihydroxy diphenyl dimethyl methane); epoxidized unsaturated fatty acid esters, particularly 4 to 12 carbon atoms or so alkyl esters of 12 to 22 carbon atom fatty acids such as butyl epoxy stearate, octyl epoxy stearate and the like; and various epoxidized long chain fatty acid triglycerides and the like, such as the epoxidized vegetable and other unsaturated natural oils (which are sometimes referred to as being epoxidized natural glycerides of unsaturated fatty acids, which fatty acids generally contain between about 12 and 22 carbon atoms) that may be specifically typified and particularized by such compositions as epoxidized soya bean oil. Many of the acid-accepting epoxy compounds are available from various sources.

Compositions that are n accordance with the invention have excellent color stability and are usually capable of providing desirably clear and light colored coatings, even after prolonged exposure to the most rigorous of hot dipping temperature elevations. Their characteristics in this regard are pronouncedly and practically astoundingly superior to ethyl cellulose compositions that are identically formulated save for the organic phosphite compound additament or the acid-accepting epoxy ingredient, or both. In addition, the incorporation of the neutral organic phosphite compound in the hot melt composition exerts an ancillary viscosity stabilizing effect that augments the marked benefit that is obtainable in this regard with the combination of 2,2'methylenebis(4 methyl-6-tert.-butyl phenol) and an acid-accepting epoxy compound.

To afford further illustration, a series of ethyl cellulose hot melt compositions were formulated and tested to determine their color stability and extent of degradation after exposure to heat at 190 C. for differing prolonged periods of time under representative conditions that may ordinarily be encountered in hot dipping operations. The compositions are set forth in the following Table I, in which composition E is formulated in accordance with the invention. The results of the color stability test are represented in Table II. The color stability of each of the compositions was evaluated by casting them into 100 mil thick films after predetermined periods of thermal exposure and observing their color characteristics both by visual examination and by measurement of their ability to transmit light having a wave length of about 450 millimicrons. A Beckmann Model B spectrophotometer was used in the light transmission tests in which greater percentages of transmitted light indicate better film color and clarity. The extent of degradation was relatively determined by measurement of the tensile strengths and elongations of the films cast from the various compositions after the thermal exposures of the hot melt compositions. According to such tests, the results of which are given in Table III, decreases in the mentioned physical properties of the films are proportionately indicative of the degree of degradation that was' undergone by the compositions from which the films were obtained during their residence at the 190 C. temperature. The elongation against thermal aging of each of the compositions is also graphically portrayed in the sole figure of the hereto-annexed drawing. In the graph, the practical limit of good pot life for a hot melt composition is indicated by a dotted line.

Table 1.-Hot melt compositions Percent By Weight In Composition Ingredient All IIB!) C UD" IIE" FII G HH" Ethyl Cellulose 25 25 25 25 25 2 25 25 "Mineral Oil 4695" b 55 5l. 4 54.9 51.2 51 51.25 54. 7 Dow Resin 27E-V9" 18 16. 8 17. 92 16. 75 16. 7 17. 92 16. 7 17.9 Parain Wax (M.P. 135 F.) 2.00 1. 80 1. 93 1. 80 1. 80 1.93 1. B 1.9 Paraplex G- i 5.0 5.0 5.0 5.0 2, '-Methylene-bis-(4-methy16tert.bnty

phen 0. 25 0. 25 0. 25 0. 25 Tricresyl Phosphite 0. 25 0. 25 0.25 0. 25

l "Standard grade having an ethoxyl content in the range from 48.0-495 percent by weight and containingl an average of 2.46-2.58 etheried ethyl substituents per glucose unit with a viscosity of about 50 centlpolses as determined by conventional test in a solvent mixture consisting of toluene and ethanol in a 4:1 volume ratio,

respectively, as obtained under the trademark Ethoceh 50 cps., std.

b A white mineral oli having Sayholt viscosities at and 210 F. of about 147.5 and 42.5 Seconds, respectively; a viscosity index of about 83; a flash point o1' about 310 F.: n specific gravity at 60 F. compared to water at the same temperature of about 0.8845; an aniline point of about 214 F.

s A polymerlzed alpha-methyl styrene product having a viscosity of 700-1,000 centipoises at 60 O.

d An ester-type epoxidized soya been oil plasticizer.

Table -Il.-Color characteristics of .100 mil vvfilms :cast `from hot melt compositions after various thermal lescgposures Heating Period of `Hot 4Melt* at 190 C.

in Hrs.

Percent v Trans- Visual Color Films From Composition Appearanceot `lliil'zn Water White. LightAmbe'r. Amber. Water White. Light Amber. Amber.

Dark Amber.l Brown.

Dark Brown. Brown.

Dark Brown. Water White. Light Amber. Water White.

Do. Light Amber. Water White.

"Brr

non

1 Apparent discrepancy in data due to visual phenomena and use of ight having narrow band of wave length iu transmission test.

Do. Light Amber. Water White. Dark Amber.

halogen substituted alkyl. phosphites, aryl phosphites, halogen4 substituted aryl phosphites, mixed .alkyl-aryl phosphites, mixed'halogen substituting alkyl-aryhphosphites. and. mixtures thereof.

.2. The composition: Aoi claim 1, containing between about 0.05 and 4.0 percent by Weight of the 2,2'methylene-bis(4.-methyl-6tert.butyl phenol); between about20 and8.0, percent by -weight of the acid-accepting epoxy compound; and between about 0.1 'and 0.5 `percent by weight of theneutral organic phosphite compound, veach basedy on the weight of the composition.

.3. A, composition .that is in accordance with the composition set'forth in claim, 2, wherein -the proportions by weight of each of saidstabili'zing ingredients are in the ratio oflabout'0'4-4z`10-#301 in the respective recited order. v

4. A .composition in vaccordance with the composition setforth in claim 3, wherein the combined total of said stabilizing ingredients is between about 4 and 7 percent by Weight of the composition.

5. The composition of claim 1, wherein the neutral organic phosphite compound is an alkyl phosphite in which the alkyl groups independently contain from 2 to 10 carbon atoms in their structures.

6. The composition of claim 1, wherein the neutral organic phosphite compound is an aryl phosphite in which various thermal exposures Films From C omp osi- --l HA!! BH C HD" En UF" UGH UH" Heating Period of Hot Men at 190 o. In T s 'r s 'r s T s T s T s 'r s 'r s Hrs. (e) (f) 41 50o 68 508 73 575 76 625 76 370 7o 37o s1 325 57 405 48 494 71 (h) (h) (h) (h) 32o 30 35o 78 10o 3 16 375 a1 50o 72 (h) (h) (h) (n) 250 s 32o 74 (g) (g) (e) s) (s) 660 73 765 85 725 75 (g) (e) 220 23 (g) (s) (g) s) (g) 730 71 750 70 742 70 gg) (s) (t) (e) 5g) (s) (e) (s) (g) (h) (h) 630 38 720 64 e) (s) (s) (s) e) (s) (s) (e) (g) (h) (h) (s) (g) 680 52 (e) (g) (g) (g) (g) (e) (s) (e) (e) 790 24 (t) (s) (g) (s) (e) (e) (e) (s) (g) (s) Zorn-(e) Indicates tensile strength of film in pounds ner square inch. (f) Indicates per cent Elongation o Film. (g) Indicates that no sample was exposed for designated period. (l1) Value not determined.

Practically the same results as above were noted when Z-ethylhexyl octylphenyl; tris-(2-chloroethyl); and triisooctyl phosphites were utilized Iin the same manner as the organic phosphate compounds and when a diglycidyl ether of a polyglycol from ethylene oxide; butyl epoxy stearate and hexyl epoxy stearate were employed as the acid-accepting epoxy ingredients. Commensurate outstandngly excellent results and literally dramatic beneiits are provided when other stablized hot melt compositions in accordance with the invention are formulated with other of the indicated species of organic phosphite compounds and acid-accepting epoxy compounds.

Although the present invention has been primarily illustrated with 2,2methylenebis(4methy1-6tert.butyl phenol), it is to be clearly understood that the invention is equally susceptible to being successfully practiced with the equivalent homologues of the indicated oxidation-inhibiting compound.

What is claimed is:

1. Ethyl cellulose hot melt composition that is stabilized with a minor proportion each of between about 0.005 and 5 weight percent, based on the weight of the composition, of (A) 2,2methylenebis (4-methyl-6-tert.- butyl phenol); between about 0.1 and 10 weight percent, based on the weight of the composition, of (B) an acidaccepting epoxy compound; and between about 0.1 and 2 weight percent, based on the weight of the composition, of (C) a neutral organic phosphite compound that is selected from the group consisting of alkyl phosphites,

the aryl groups independently contain from 6 to 16 carbon atoms in their structures.

7. The composition of claim 1, wherein the neutral organic phosphite compound is an alkyl-aryl phosphite in which each alkyl group and each aryl group independently contains from 2 to l0 and from 6 to 16 carbon atoms, respectively, in its structure.

8. The composition of claim 1, wherein the neutral organic phosphite compound is tricresyl phosphite.

9. The composition of claim 1 wherein the neutral organic phosphite compound is 2ethylhexyl octylphenyl phosphite.

10. The composition of claim l, wherein the neutral organic phosphite compound is tri-(2-ch1oroethyl) phosphite.

11. The composition of claim 1, wherein the neutral organic phosphite compound is triisooctyl phosphite.

l2. The composition of claim l, wherein the neutral organic phosphite compound is tris-(2-ethylhexyl) phosphite.

13. The composition of claim l wherein the acid-accepting epoxy compound is a diglycidyl ether of a poly-- glycol.

14. The composition of claim 1, wherein the acid-accepting epoxy compound is a diglycidyl ether of bisphenol A.

15. The composition of claim 1, wherein the acid-accepting epoxy compound is an epoxidized unsaturated fatty acid ester.

`16. A compositionaccordingto the composition set forth inoilaim` 15, wherein `theacid-accepting epoxy conl pound is octyl epoxystearate.' 'Y y 17. A composition according to the composition set forth in claim 15, wherein the acid-accepting epoxyvcomj pound is butyl epoxy stearate.

18. The composition of claim 1, wherein the acid-accepting epoxy compound is an epoxidized natural glycer-I ide of unsaturated fatty acids, which fatty acids contain from 12 to 22 carbon atoms in their structures. 19. A composition according to the composition set forth in claim 18, wherein the acid-accepting epoxy compound is epoxidized soya bean oil.

References Cited in the lc of this patent UNITED STATES PATENTS `8 Krieger Oct. `20, 1942 Pratt June 15, 1943 Koch Nov. 2, 1943 Sharphouse et al Aug. 12, 1947 JI-Iorlvack Feb. 3, 1951 1 Stevens et al; Oct. 9, 1951 Shokal Mar. 31, 1953 Bcko Sept. 8, 1953 Thompson June 14, 1955 Shokal Ian. 24, 1956- Carlson Mar. 20, 1956 Petropoulos July 10, 1956' 

1. ETHYL CELLULOSE HOT MELT COMPOSITION THAT IS STABILIZED WITH A MINOR PROPORTION EACH OF BETWEEN ABOUT 0.0005 AND 5 WEIGHT PERCENT BASED ON THE WEIGHT OF THE COMPOSITION OF (A) 2,2''-METHYLENE-BIS (4-METHYL-6-TERT BUTYL PHENOL): BETWEEN ABOUT 0.1 AND 10 WEIGHT PERCENT BASED ON THE WEIGHT OF THE COMPOSITION, OF (B) AN ACIDACCEPTING EPOXY COMPOUND; AND BETWEEN ABOUT 0.1 AND 2 WEIGHT PERCENT, BASED ON THE WEIGHT OF THE COMPOSITION OF (C) A NEUTRAL ORGANIC PHOSPHITE COMPOUND THAT IS SELECTED FROM THE GROUP CONSISTING OF ALKYL PHOSPHITES. HALOGEN SUBSTITUTED ALKYL PHOSPHITES, ARYL PHOSPHITES, HALOGEN SUBSTITUTED ARYL PHOSPHITES, MIXED ALKYL-ARYL 